This invention relates broadly to the field of medical devices known generally as bone distractors, which are devices designed to allow the distance between two bone segments to be gradually increased while bone regenerates in the area between the bone segments. In particular, the invention relates to cranial bone distractors, which are devices applied to two bone segments of the cranium. The distractors comprise in general a pair of bone plates mounted to a distraction assembly.
Bone regeneration or osteogenesis is a medical technique for repairing defective or damaged bones, such as for example when a bone fails to fully develop to its proper shape or size. An osteotomy or cut is made in the bone to produce two sides of exposed bone tissue and a distractor mechanism is attached to both bone segments. As new bone tissue is produced by the bone segments to bridge the gap, the distractor mechanism is used to gradually increase the distance between the bone segments. New bone tissue continues to be produced and eventually the proper shape or size for the bone is achieved. The distractor mechanism is then removed and the bone is allowed to heal and rigidify.
Bone distractors are well known in the art, but are primarily designed for linear distraction. Linear distraction is suitable for many bones, such as the mandible or the long bones of the legs or arms, but is not optimal for bones possessing curved topographical configurations, such as for example the cranium. A problem with known distractors when used with cranial distraction is that the linear distractors fail to accommodate the curvature of the cranium, such that the distraction does not result in formation of new bone having or approximating the appropriate curvature, instead producing a more planar area of new bone. It is an object of this invention to provide a cranial distractor that addresses this problem, wherein the distraction mechanism has a linear operation but the bone plates affixed to the opposing bone segments are mounted in a manner allowing free multi-directional movement to allow and account for the curvature and changes in the topography of the cranium during the osteogenesis process.